(a) Technical Field
The present disclosure relates to a fail-safe device and a fail-safe method for an engine clutch actuator for a hybrid vehicle. More particularly, it relates to a fail-safe device and a fail-safe method for an engine clutch actuator for a hybrid vehicle, which facilitate conversion from an electric vehicle (EV) mode to a hybrid electric vehicle (HEV) mode when an actuator for a dry type engine clutch fails, and enable synchronization between an engine and an engine clutch to be performed by operating the engine in advance.
(b) Description of the Related Art
A hybrid vehicle, which is a kind of environmentally-friendly vehicle, may implement various power transmission structures using an engine and a driving motor as power sources, and usually includes driving modes such as an EV mode in which the vehicle travels using only driving power of the driving motor, and an HEV mode in which the vehicle travels using driving power from both the engine and the driving motor.
The HEV mode in which the vehicle travels while power from the engine is output together with power from the driving motor is implemented at the time of engaging an engine clutch disposed between the engine and the driving motor, and the EV mode in which power of the engine is shut off and the vehicle travels using only power from the driving motor is implemented at the time of disengaging the engine clutch.
In a case in which a dry type engine clutch is applied as the engine clutch, a separate engine clutch actuator for operating the engine clutch is mounted in order to perform conversion into the HEV mode or the EV mode, and the engine clutch actuator (E/C ACT) is applied to a hybrid system that is provided based on a dual clutch transmission (DCT).
Hereinafter, a configuration of an engine clutch actuator in the related art will be described with reference to FIG. 1 (RELATED ART).
In FIG. 1 (RELATED ART), reference numeral 10 indicates an engine clutch actuator that uses electricity and hydraulic pressure.
The engine clutch actuator 10 is disposed between an engine 30 and a driving motor 40, and serves to engage an engine clutch 20 with an engine side in the HEV mode that is performed using power from both the engine and the driving motor. In contrast, in the EV mode that is performed using only power from the driving motor, the engine clutch actuator 10 serves to disengage the engine clutch 20 from the engine side.
An electric motor 11 is disposed at one side of the engine clutch actuator 10, and an actuator master cylinder 14 is disposed at the other side of the engine clutch actuator 10.
A screw shaft 12 is adopted as an output shaft of the electric motor, and a rectilinearly movable block 13 is fastened to the screw shaft 12 in an inserted manner.
In addition, a first piston 15 is disposed in the actuator master cylinder 14, and a back side of the first piston 15 is connected with the rectilinearly movable block 13 by a piston rod.
The actuator master cylinder 14 is connected with a concentric slave cylinder 17 by a hydraulic pipe 16 so as to exchange the hydraulic oil with the concentric slave cylinder 17.
A second piston 19 is disposed in the concentric slave cylinder 17, the second piston 19 is connected with a pressing plate 18 by a piston rod, and the engine clutch 20 is mounted on the pressing plate 18.
In this case, a flywheel 21 of the engine is positioned at a side that faces the engine clutch 20.
Hereinafter, an operation flow of the engine clutch actuator having the aforementioned configuration will be described.
Conversion from HEV Mode to EV Mode
First, a local control unit (LCU), which receives a signal from a hybrid control unit (HCU), operates the electric motor 11.
Therefore, the screw shaft 12 is rotated in a forward direction by the operation of the electric motor 11, and the rectilinearly movable block 13 is rectilinearly moved in a forward direction.
Consecutively, the rectilinearly movable block 13 pulls the first piston 15 in the actuator master cylinder 14 in the forward direction, and at the same time, the second piston 19, which is moved in a rearward direction by elastic restoring force of a return spring, presses the hydraulic oil in the concentric slave cylinder 17, such that the hydraulic oil is supplied into the actuator master cylinder 14 through the hydraulic pipe 16.
In this case, as the second piston 19 is moved in the rearward direction, the engine clutch 20 connected with the pressing plate 18 is separated from the flywheel 21 of the engine, and as a result, the engine clutch is in a disengaged state.
When the engine clutch is in the disengaged state as described above, the vehicle travels in the EV mode that uses only power from the driving motor instead of using power from the engine.
Conversion from EV Mode to HEV Mode
The screw shaft 12 of the electric motor 11 is rotated in a reverse direction, and the rectilinearly movable block 13 is rectilinearly moved in the rearward direction.
Consecutively, the rectilinearly movable block 13 pushes the first piston 15 in the actuator master cylinder 14 in the rearward direction, and at the same time, the hydraulic oil in the actuator master cylinder 14 is supplied into the concentric slave cylinder 17 through the hydraulic pipe 16 by pressing force of the first piston 15.
Consecutively, the hydraulic oil supplied into the concentric slave cylinder 17 pushes the second piston 19 in the forward direction, such that the second piston 19 is moved forward while compressing the return spring, and pushes the pressing plate 18.
Therefore, the engine clutch 20 connected with the pressing plate 18 is coupled to the flywheel 21 of the engine, and as a result, the engine clutch is in an engaged state.
When the engine clutch is in the engaged state as described above, the HEV mode in which the vehicle travels using power from both the engine and the driving motor is implemented.
As described above, the dry type engine clutch is engaged or disengaged by the engine clutch actuator, such that the HEV mode or the EV mode may be easily implemented.
In a case in which the electric motor cannot be operated, that is, the electric motor fails because of various reasons such as burnout of the electric motor of the engine clutch actuator or disconnection of lines for supplying electric power to the electric motor when the vehicle travels in the EV mode as described above, a controller may determine that it is difficult to allow the vehicle to continuously travel in the EV mode, and may apply logic for commanding the conversion into the HEV mode.
However, because the rectilinearly movable block 13, and the first piston 15 in the actuator master cylinder 14 as well as the screw shaft 12 cannot be moved due to the failure of the electric motor, the hydraulic oil in the actuator master cylinder 14 cannot be supplied into the concentric slave cylinder 17, and as a result, there is a problem in that the engine clutch cannot be engaged, and the conversion into the HEV mode cannot be properly performed.
Particularly, if the engine is not operated even when the driving mode is converted from the EV mode to the HEV mode, there is a problem in that a large amount of vibration and noise may occur due to a collision between the engine in a stationary state and the engine clutch that is connected with the driving motor and rotated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.